The commerical production of crystalline D-glucose and high glucose syrups from starch is generally carried out by an enzymatic process using glucoamylase of fungal origin, particularly enzyme preparations derived from fungi of the Aspergillus and Rhizopus genera. A preferred method of producing this enzyme involves the fermentation in an appropriate nutrient medium of an organism from the species A. niger. Glucoamylase hydrolyzes both .alpha.-D-(1.fwdarw.4) and .alpha.-D-(1.fwdarw.6) glucosidic bonds of starch. Hydrolysis by glucoamylase of .alpha.-D-(1.fwdarw.4) bonds occurs substantially faster than the rate of hydrolysis of .alpha.-D-(1.fwdarw.6) bonds. It has been known for many years that the culture filtrate from A. niger fermentations contain a second enzyme, transglucosidase (TG) which is capable of transferring glucosyl residues from sugars containing .alpha.-D-(1.fwdarw.4) or .alpha.-D-(1.fwdarw.6) glucosidic linkages to the 6-position of other sugar molecules. The formation of .alpha.-D-(1.fwdarw.6) linkages causes a marked decrease in the glucose yield during the enzymatic conversion of starch.
Because of the reduction in glucose yield caused by the presence of transglucosidase in glucoamylase preparations, techniques have been developed to remove this contaminant. One technique is disclosed in U.S. Pat. No. 3,042,584 in which a fungal amylase preparation containing transglucosidase and glucoamylase activities is contacted with a clay mineral. This procedure results in selective adsorption of transglucosidase by the clay thereby facilitating separation of the enzymes by liquid/solid separatory techniques.
Before any such separation of enzymes is attempted and for quality control of finished glucoamylase product, it is essential to be able to determine the level of transglucosidase in the glucoamylase preparation that is to be or has been treated. One method for the determination of transglucosidase activity is disclosed in the aforementioned '584 patent. This method is based on the conversion of maltose into glucose by the glucoamylase preparation under test. The extent of conversion is determined by comparing the optical rotation of the product produced by the glucoamylase preparation under test with that produced by a standard (TG-free) glucoamylase preparation. The presence of TG results in a product with higher specific rotation than that produced under identical conditions by glucoamylase free of TG. This method suffers from the disadvantage of being slow (requiring 72 hours to complete) and it is not quantitative because the two enzymes (glucoamylase and transglucosidase) compete for the same substrate (maltose).
It would be desirable, and it is an object of the present invention, to provide a quantitative, rapid method for the determination of transglucosidase activity, particularly one that can be used for measurement of TG activity in enzyme preparations containing both glucoamylase and transglucosidase activity.